Custom text for your video goes here. You can always copy and paste whatever text you have for this video from the Youtube site or put in new text.
Since this video is within a gallery you have the option of turn on the "Comments" feature.
You can also schedule when this video is published. Meaning you can work on it ahead of time and set a custom publishing time for when it appears on your website. Click on the "Draft" button in the window that pops up when you add a new video to see your options.
Also remember to make make a distinction between clicking "Save & Publish" and just "Save". If the video is marked as DRAFT, no matter how many times you save it, it won't appear to the public.
You also have the option of adding "tags" or "categories". This feature is useful later on if you decide to add a search bar, or if you want to have a tag cloud.